Solar cells are well known devices for converting solar radiation to electrical energy. A solar cell has a front side that faces the sun during normal operation to collect solar radiation and a backside opposite the front side. Solar radiation impinging on the solar cell creates electrical charges that may be harnessed to power an external electrical circuit, such as a load.
A photovoltaic panel, which is also referred to as a photovoltaic module, comprises a string of solar cells that are packaged together on a common support structure, such as a frame. A photovoltaic system may comprise one or more photovoltaic panels that form an array of solar cells. Photovoltaic systems may be installed in a residential housing, commercial building, or power plant as a green energy source. Because a photovoltaic panel generates power as long as its solar cells receive solar radiation, the photovoltaic panel's output voltage may pose a hazard to firefighters or other personnel who may have to be near the photovoltaic panel in the event of an emergency. The 2017 National Electric Code (NEC) Section 690.12 introduces a requirement for rooftop photovoltaic systems to limit controlled conductors to 80V or less within the array boundary and to 30V or less outside of the array boundary within 30 seconds of initiation of a rapid shutdown of the photovoltaic system.